Method of and apparatus for bending workpieces by pushing them into a curved die-cavity



July 22, 1958- w. L. ENGHAUSER ,8 85

METHOD OF AND APPARATUS FOR BENDING WORKPIECES BY PUSHING THEM INTO ACURVED DIE-CAVITY Filed March 9, 1954 5 Sheefs-Sheet 1 INVEN TOR.

A T TOENE Y5 July 22, 195 w. ENGHAUSER 2,844,185

METHOD OF AND AP A ATUS FOR BEINDING WORKPIECES BY PUSHING THEM INTO ACURVED DIE-CAVITY File'd March 9, 1954 3 Sheets-Sheet 2 IN V EN TOR.

ATTORNEYS.

W. L; ENGHAUSER METHOD OF AND APPARATUS FOR BEND 81 5 99 h Y 2 2m n E sI P 3 K R 0 w G N I BY PUSHING THEM'INTO A CURVED DIE-CAVITYllllllllllllllllll|b|\ INVENTOR.

ATTORA/E ys.

United States Patent NlETHOD OF AND APPARATUS FOR BENDING WORKPIECES BYPUSH-TING THEM INTO A CURVED DIE-CAVITY Winford L. Enghauser,Cincinnati, Ohio, assignor to Enghauser Manufacturing Company, Inc., acorporation of Ohio Application March 9, 1954, Serial No. 414,953

Claims. (Cl. 153-48) This invention relates to a die for imparting aconvolute or sinuous form to a straight length of metal tubing or barstock and is intended particularly for forming ornamental iron pieces ormechanical parts to a desired length configuration. The inventioninvolves method and apparatus aspects, both relating to the bending oflengths of stock to a curved configuration.

One of the primary objects of the invention has been to provide a diewhich may be used with a conventional die press to bend successiveworkpieces to a simple or complex lineal configuration at a rapid,economical production rate.

Machines for bending bar stock, tubes and pipes are Well known and havebeen used for many years. One class of such machines utilizes theprinciple of bending the stock progressively around a forming blockhaving the desired curve formation. The stock may be forced around theforming block by a shoe member attached to a swinging arm, or theforming block may be forced against an intermediate portion of the stockwhile the end portions of the stock are engaged against stops. Inanother type of equipment, the stock is formed between fixed and movabledies mounted in a press, the two dies having complementary curved facesarranged to bend the stock as the two dies are forced toward oneanother. These structures necessarily are limited to the formation ofregular curves, or a combination of curves and straight sections offairly simple design.

The present invention is intended for bending lengths of cylindricalstock to relatively irregular curves, which may extend through an aregreater than 180 degrees, for example, generally spiral or sinuous formswhich are diflicult to reproduce with conventional methods or apparatus.Briefly, the invention involves the use of a die having an elongatedcavity or passageway which is generally convolute along its length, thelength of stock being forced under pressure lineally into an open end ofthe cavity so as to progressively reproduce the configuration of thecavity in the length of stock. The longitudinal curvature of the diecavity preferably extends through an are substantially greater than 180degrees of a circle inscribed about the die cavity. The cavity is openalong one side throughout its length and the die includes a closureplate which resides along the open side of the cavity, the closureplatebeing shiftable laterally for removing the workpiece after it has beenformed in the cavity. In other words, since the cavity imparts itslineal configuration to the length of stock, the stock must be dislodgedlaterally from the cavity after it is formed.

As applied to the bending of tubular stock such as pipe,

which is circular in cross section, the cavity preferably is square incross section and loosely confines the pipe about four sides. Thisprovides fiat lineal bearing surfaces tangent to the cylindrical surfaceof the stock at four sides for guiding the stock with the least possiblefrictional resistance as it is forced longitudinally through the diecavity. The surface of the closure plate delineates one of the fourwalls of the cavity to simplify the Patented July 22, 1958 constructionof the die assembly. In another form, the cavity is circular in crosssection and is delineated by a pair of semi-circular grooves formed inthe die and closure plate and mating with one another. The die ismounted in fixed position upon a base plate and the closure plate isslidably mounted upon the base plate for movement laterally to and fromthe open side of the cavity. Actuating means, which may be hand or poweroperated, shifts the closure plate relative to the die cavity and clampsit under pressure against the die in closed position to confine thestock as it is forced into the cavity. For the purpose of illustratingthe principle of operation, a hand operated cam is disclosed as themeans for actuating and clamping the closure plate; however, it will beapparent that a power actuated clamp structure may be used. i

In operation, the die assembly is mounted directly upon the platen ortable of a press with the open end of the cavity exposed at the topsurface of the die assembly. The straight length of stock is insertedinto the open end of the cavity and is forced lineally into the cavityupon downward motion of the ram of the press or by upward motion of thetable, depending upon the type of press. After the stock is formed, theram is elevated, the closure plate is retracted for removal of theformed piece and the closure plate is shifted back to closed positionfor the next operation, thus allowing the successive pieces to be formedat a rapid production rate. The die is useable with practically any typeof press which has a stroke of sufficient length to accommodate thelength of the workpieces and sufficient power to form them.

Various other features and advantages of the invention will be morefully apparent to those skilled in the art from the following detaileddescription taken in conjunction with the drawings.

In the drawings:

Figure 1 is a side elevation of the die assembly in closed position.

Figure 2 is a top plan view projected from Figure 1, showing the die inopen position for removal of the formed length of stock.

Figure 3 is a fragmentary top plan View similar to Figure 2, showing thedie in closed position.

Figure 4 is an end view of the die assembly.

Figure 5 is a cross sectional view taken on line 55, Figure 2,illustrating the face of the cam which actuates the closure plate of thedie assembly.

Figure 6 is a longitudinal sectional view taken along line 66, Figure 2.I

Figure 7 is a sectional view taken along line 7-7, Figure 2, detailingthe forming plate of the die.

Figure 8 is a diagrammatic view of the die, showing a length ofstockbeingforced therein by the ram of a press.

Figure 9 is a top plan View illustrating a die assembly of slightlymodified construction.

Figure 10 is a side view illustrating the workpiece after being ejectedfrom the die.

Described generally with reference to Figures 1 and 2, the die assemblyis of Welded construction consisting of a base plate 10 having a pair ofmounting blocks 11 and 12 rising upwardly from its opposite endportions. The block 12 supports the forming plate assembly which isindicated generally at 13 and the second block 11 movably carries aclosure plate assembly 14 which is shifted to an open or closed positionrelative to the forming plate as shown in Figures 1 and 2. The formingplate which determines the shape to be imparted to the workpiece.

In the present disclosure, the cavity is generally convolute as viewedin Figures 7 and 8, the cross section of the cavity being generallysquare (Figure 3). In this example, the longitudinal curve of the cavityis irregular and the arc of the curve decreases progressively in theform of a spiral from the open end towards the closed end of the cavity.The degree of curvature from the open end to the closed end of thecavity is indicated diagrammatically as the are A of a circle inscribedabout the cavity. It will be noted in the example, that the are Aextends approximately three quarters around the inscribed circle, beingsubstantially greater than 180 degrees. The open end of the cavity atthe top of the forming plate includes a straight portion indicated at 16to facilitate the entry of the stock, such as the cylindrical tube orrod 17 illustrated in the drawings. With the die in closed position, thelength of stock is forced axially into the cavity by the ram of thepress (Figure 8), causing the leading end of the stock to follow thecurving passageway delineated by the cavity. The length of stock thus isprogressively bent to a spiral or convolute shape corresponding to thecavity. When the leading end of the stock engages the end 18 of thepassageway the forming operation is complete. At this point the ram 20is retracted and the closure plate is shifted to its open position shownin Figure 2, allowing the formed part to he slipped laterally from theopen side of the cavity.

In a production operation, the base of the die is mounted upon the bedor platen of a conventional press, the ram being movable vertically inalignment with the open end of the cavity. The stock is cut to therequired length and the pieces are placed endwisely into the open end 16of the cavity, with the ram in its elevated position above the upper endof the stock. A suitable lubricant may be applied to the stock or to thedie passageway to reduce frictional resistance as the stock is forcedthrough the passageway by the ram. As described later in detail, the dieassembly may include a manually operated lever 21 for opening andclosing the die. This lever is swung to closed position during theforming operation and is shifted to open position at completion of theoperation to allow the formed workpiece to be removed.

Described in detail, the base plate consists of a relatively heavy platewhich may be clamped in the usual manner upon the bed of the press. Themounting blocks 11 and 12 preferably are welded directly to the topsurface of the base plate as indicated at 22. The blocks 11 and 12 eachinclude a reinforcing web 23 which is welded to the surface of therespective blocks and mounting plate to resist the forces tending toseparate blocks 11 and 12 during the forming operation.

Mounting block 12 carries upon its inner face a spacer plate 24 and aforming plate 25 which, as best shown in Figure 7, includes the cavityor forming passageway 15. The cavity as disclosed, is machined as anopen curved slot completely through the forming plate, one side of thecavity being enclosed by the spacer plate 24 and the other side by theclosure plate 14 when in closed position. The forming plate preferablyis fabricated from tool steel suitably hardened to resist wear. Thespacer plate 24 and closure plate 14, which are subjected to less wear,may be fabricated from hardened steel but need not be of the samehardness as the forming plate. The active surfaces of the plates areground to a smooth finish to facilitate the passage of the stock into.the cavity.

As best shown in Figure 7, the forming :plate and spacer plate areattached to the mounting block by means of the screws 26 having headscountersunk in the forming plate. The shanks of the screws pass throughboth plates and are threaded into the mounting block 12 as indicated inbroken lines in Figure 1. In addition to the screws, a series of dowelpins 27 pass through the assembled plates and mounting block to maintainthem in accurate alignment with one another. In order to sustain theforming and spacer plates under the force imposed by the ram during theforming operation, a block 28 is interposed between the base plate andlower edge of the forming and spacer plates. The block transmitsthe rampressure directly from the forming plate to the basev plate which isseated upon the table of the press.

The closure plate assembly 14 is mounted for axial motion along theshaft 30 which projects from mounting block 11 toward the forming plateassembly. Mounting block 11 includes a boss 31 welded as at 22 to theexternal surface of the block and to the upper end of the reinforcingweb 23. The outer end portion of shaft 30 is press fitted into a borewhich is common to the block 11 and boss 31. The closure plate assemblyis mounted for axial movement along the shaft upon a backing plate 32which includes a boss 33 welded as at 22 to the surface of the backingplate on the side opposite the closure plate. The closure plate isattached to the backing plate by the screws 34 having their headscountersunk in the closure plate similar to the screws 23 (Figures 1 and5).

The closure plate assembly is slidably mounted upon shaft 30 formovement to its open and closed positions by means of a cam 35 which ismounted for rotation upon shaft 30. The cam is rotated by lever 21 whichprojects outwardly from the cam. The boss 33 of the closure plateassembly includes a non-rotatable cam 36 at its outer end which iscomplementary to the surface of cam 35. The closure plate assembly 14and its cam 36 are non-rotatably keyed to the shaft by the keys 37-37fixed to the boss 33 and slidably interfitting the keyways 38 formed inthe shaft. Rotation of the cam 35 is effective to shift the closureplate assembly axially along shaft 30 while the keys 37 prevent theassembly and its cam 36 from rotating.

The rotatable cam is confined against axial motion by a retainer block38 which is attached to the mounting block 11 by the screws 40 and dowelpins 41 (Figure 2). The retainer block includes an opening having anannular lip 42 which overhangs the annular flange 43 of the rotatablecam. The flange 43 thus is confined against axial motion between theoverhanging'flange and the surface of the mounting block 11 as shown inFigure 6. Suitable clearance, as indicated at 44, is provided around theperiphery of the cam.

Referring to Figure 5, theface of cam36 is provided with two flats 45and 46 which are located at diametrically opposite sides as indicated.As viewed in Figure 2, the flats are located in planes which are spacedfrom one another along the axis of shaft 30, the flats being joined bythe inclined camrning surfaces indicated at 47 and 48 on respectivelyopposite sides. The faces of the fixed cam and rotatable cam arecomplementary to one another and nest together when the rotatable .camis positioned to retract the closure plate (Figure 2). When theactuating lever 21 is swung in closing direction, the inclined cammingsurface of the rotatable cam 35 advances or planes relative to theinclined camming surface of the non-rotatable cam 36, causing cam 36 andits associated closure plate assembly to be shifted toward the formingplate. Upon rotation of approximately one half turn, the flat 45a'of therotatable cam, advances toward and over the, flat 45 of thenon-rotatable cam, the closure plate having thus been shifted intopressure engagement against the surface of the forming plate as shown inFigure l.-' In closed position, the actuating lever 21 is in theposition shown in broken lines in Figure 2. It will be evidentthatuponfacial engagernent with one another, the two flats 45 and 45a clampthe closure plate assembly rigidly against the forming plate towithstand the pressure tending to separate the two plates as the stockis forced lineally into the cavity.

After the bending operation, the lever 21 is swung back to the positionshown in Figure 2 and the closure plate assembly is shifted to itsretracted position by the compression springs 50. As shown in Figure 7,these springs are located at diagonally opposite corner portions of theforming plate assembly and are confined in bores 51 extending throughthe plates. Each spring is seated against a plate 52 attached by screws53 to the mounting block 12. The opposite end of each spring is seatedagainst the end of a bore 54 formed in the face of'the closure plate. 7

The lower end of the ram 20 is provided with a pressure plate 55 whichincludes a central boss 56 projectingdownwardly (Figure 8). Centrally ofthe boss there is provided a bore 57 having a diameter corresponding tothe stock 17 to confine the upper end of the stock as it is forced intothe die cavity. The bore 57 is coaxial with the open end 16 of thecavity such that the stock is confined against lateral displacement. Theforming pressure is indirect thrust or compression upon the stock so asto'drive it into the cavity without imposing buckling forces upon theportion of the stock projecting from the die. It will be noted that thestraight portion 16 of the cavity allows the stock to be placedpartially in the die cavity without pressure so as to facilitate thestart-of each operation.

The die assembly lends itself to rapid production of workpieces sincethe operator may place the lengths of stock rapidly in the open end ofthe cavity with the ram elevated, initiate press operation and removethe finished workpieces in rapid sequence. Following conventionalpractice, the press may be equipped with an automatic control systemincluding power means for opening and closing the closure plate inresponse to the position of the ram. For this purpose it is contemplatedto utilize a power motor, such as an air cylinder, to shift the closureplate to its open and closed positions instead of the cam structure.Since mechanism of this type is well known, it has been omitted from thedrawings.

It will be understood that the press may be of the type having a movabletable and a fixed stop member as distinguished from the movable ramdisclosed in the present example. In this case the forming operation isidentical except that the die assembly is moved toward the fixed stopduring the forming operation.

The spiral form of the elongated cavity illustrated in the drawings isselected to illustrate the operating principles of the invention. Itwill be understood that the cavity takes various other forms as dictatedby the shape to be imparted to the stock. The desired configuration ismachined as an open slot in the forming plate, such as by a millingoperation; thereafter, the forming plate is hardened, ground andattached to the spacer plate as described earlier. When utilizing a diecavity having a curvature extending substantially beyond an arc of 180degrees, as shown in Figure 8, the frictional resistance to theadvancement of the stock increases sharply as the length of stock curvesbeyond 180 degrees. Moreover, the resistance is further increased as thespiral curvature increases toward the closed end of the die. However,the flat lineal bearing surfaces of the die cavity reduces the frictionsufliciently to make it possible to bend the stock without requiringundue pressure or causing collapse of the walls of the tube. It will beunderstood that the stock is forced longitudinally into the cavity untilits leading end contacts the closed end 18 of the cavity. The closed endthus controls the bending operation and makes it possible to bendsuccessive lengths of stock to identical configuration.

The die assembly shown in Figure 9 is similar to the structure alreadydescribed except that the cavity is cylindrical in cross section insteadof square. The cavity is constituted by a pair of complementalsemi-circular grooves 58 let into the surface of the forming plate 25and closure plate 14. The cylindrical cavity is intended particularlyfor thin walled tubing since it creates a slightly different bendingaction by embracing the cylindrical stock around its entire periphery.In bending thin walled tubular material around a relatively sharp curve,there is a tendency for the tube to collapse more or less at the bend,depending upon the ductility of the material and other factors. As thetube begins to collapse, it necessarily becomes wider along the sides atright angles to the collapsing area. By confining the tube wall for itsfull circumference in the cavity, the wall is restrained againstexpanding and hence is supported against collapse. The cylindricalcavity also has the advantage of providing rapid dislodgrnent of theformed workpiece when the cavity is opened.

As outlined earlier, the die structure is intended particularly forworking tubular stock such as iron pipe which is cylindrical in crosssection. These parts are used in ornamental iron work, for example,railings, support columns for porches and other structures having thecharacteristics of wrought iron. The workpiece illustrated in Figure 10represents such a workpiece formed in the illustrated die cavity. In thepresent disclosure, the workpiece consists of iron pipe, which isprovided with closed rounded ends as indicated at 68) for appearance andweather protection. The end 18 of the die cavity is similarly roundedand the bore 57 of the pressure plate has a tapered end wall conforminggenerally to the rounded pipe end. It will be understood that theinvention can also be applied to the formation of stock having a squareor other form of cross section and may be either solid or hollow.

Having described my invention I claim:

1. A die arranged to be mounted upon a press having a relatively movabletable and ram, the die adapted to bend a straight length of cylindricalmetal stock to a generally curved form along its length, said diecomprising a base adapted to be mounted upon the table of the press, adie mounting member rising at right angles from said base, a formingplate attached to the mounting member, said forming plate having anelongated open slot formed therein, said slot comprising a pair of fiatbearing surfaces spaced apart from one another residing in right anglesto the plane of the forming plate, and extending to the upper edgethereof, said slot being generally curved along its length and providinga die cavity, said mounting member having a flat face enclosing one sideof the slot, the other side being open, a closure plate having a flatface, support means on the base connected to the closure plate shiftablysupporting the same for movement relative to the forming plate, keymeans on said support means slidably engaging the closure plate andlocking the closure plate against rotary motion relative to the formingplate, said closure plate engaging the forming plate at the open side ofsaid slot to enclose the diecavity, said cavity being generally squarein cross section providing fiat bearing surfaces tangent to thecylindrical stock about four sides thereof, the cavity having an openend portion at the upper edge of the forming plate, the longitudinalcurvature of the die cavity residing in a flat plane and extendingthrough an arc substantially greater than degrees of a circle inscribedabout the longitudinal cavity, compression spring means interposedbetween the closure plate and forming plate, and actuating meansconnected to the closure plate for forcing the same against the formingplate counter to said compression spring means, the open end portion ofsaid slot being elfective to receive and confine an end portion of thestraight length of stock with the stock projecting outwardly toward theram of the press, there by to be forced lineally into the cavity uponrelative movement of the ram and table, the actuating means releasingthe closure plate for movement by the compression spring means from theforming plate for removing the formed stock from theopen side of theslot.

2. The method .of cold bending a straight length of cylindrical metalstock longitudinally to an irregularly curved form which extends throughan arc greater than 180 degrees, said method consisting of introducingthe end portion of the length .of cylindrical stock into an open end-ofa longitudinal die cavity which is curved longitudinally from said openend to a closed opposite end and having a coextensive opening along oneside, said curvature extending through an are greater than 180 degreesof ;a circle inscribed about the longitudinal cavity and about theopposite ends thereof, forcing a cover element against the co-extensiveopening along one side of said longitudinal die cavity,':thereby closingthe longitudinal die cavity, said closed .die cavity having in crosssection a plurality of flat surfaces which are tangential to thecylindrical metal stock, said flat surfaces providing line bearingsurfaces for guiding the stock longitudinally through the die cavity,applying sufiicient :pressure upon the outer end of the stock to forcethe same longitudinally through the open end of the die cavity andconcurrently bending the stock toward said degree. of curvature greaterthan 180 degrees, continuing to force the stock through the cavity untilits leading end advances into abutment with said closed opposite end,thereby to bend the length of stock to the curvature of the longitudinalcavity, and removing the formed stock laterally from the coextensiveopening of the die cavity.

3. The method of cold bending a straight length of cylindrical metalstock longitudinally to an-irregularly curved form which extends throughan are greater than 180 degrees, said method consisting ofintroducingthe end portion of the length of cylindrical stock into anopen end of a longitudinal diecavity which is. curved longitudinallyfrom said open end to a closed opposite end and having a coextensiveopening along one side, said curvature extending through an are greaterthan 180 degrees of a circle inscribed about the longitudinal cavity andabout the opposite ends thereof, the die cavity being generally squarein cross section providing fiat surfaces tangent to the cylindricalstock surface at four sides thereof, said flat surfaces providing linebearing surfaces for guiding the stock longitudinally through thecavity, applying suificient pressure upon the outer end ofthe stock toforce the same longitudinally through the open end of the die cavity andconcurrently bending the stock toward said degree of curvature greaterthan 180 degrees, continuing to force the stock through the cavity untilits leading end advances into abutment with said closed opposite end,thereby to bend the length of stock progressively to the curvature ofthe longitudinal cavity, and removing the formed stock laterally fromthe said coextensive opening of the die cavity.

4. The method of cold bending a straight length of cylindrical metalstock longitudinally to an irregularly curved form which extends throughan arc greater than 180 degrees, said method consisting of introducingthe end portion of the length of cylindrical stock into an open end of alongitudinal die cavity which is curved longitudinally frorntsaid openend to an opposite end and having a coextensive opening along one side,said curvature extending through an are greater than degrees of a circleinscribed about the longitudinal cavity and about the opposite endsthereof, forcing -.a cover element having .a flat face :against theopening along one side of the dieeavity,:the enclosed die cavity beinggenerally square in cross section providing flat surfaces tangent to thecylindrical stock surface and providing line bearing surfaces forguiding the stock longitudinally through the cavity, applyingsufiicientpressure upon the outer end of the stock to force the samelongitudinally through the open end of the die cavity and concurrentlybending the stock toward saiddegree of curvature greater than 180degrees, continuing to force the stock through the cavity until itsleading end, advances to said opposite end, thereby to bend the lengthof stock progressively to the curvatureof the longitudinal cavity,removing the cover element from the said coextensive opening, andremoving the formed, stock laterally from the opening of the cavity.

5. ,A .die arranged to be mounted upon a press having a relativelymovable table and ram, the die adapted to bend astraight length ofcylindrical metal stock longitudinally to an irregular curvatureextending through an are greater than 180 degrees, said die comprising abase adapted tobe mounted upon the table of the press, a formingplatevrising at right angles from said base, said forming plate having a fiatmeeting face and having a longitudinal slot therein, said slot havingflat spaced side Walls joined by a right angular bottom, said slothaving an open end at the upper edge of the forming plate and a closedopposite end, the spaced side walls of the slot being irregularly curvedlongitudinally from said open end 'to said opposite closed end, saidcurvature extending through an are greater than 180 degrees of a circleinscribed about the longitudinal slot, a closure plate having a fiatmeeting face, means securing the closure plate to the forming plate withsaid meeting faces engaged against one another, thereby covering' theopen side of said slot and providing a die. cavity which is generallysquare in cross section, the open end of the die cavity therebybeing'etfective to receive and confine an end portion of the stock withthe stock projecting outwardly toward-the ram of the press to beforcedlongitudinally into the cavity to the closed end thereof upon relativemovement of the ram and table.

References Cited in the file of this patent UNITED STATES PATENTS 15,851Kilburn et 'al. Oct. '7, 1856 1,901,897 Clayton Mar. 21, 1933 1,978,452Flodin Oct. 30, 1934 2,183,702 Wendel Dec. 19,1939 2,335,342 KavarnstromNov. 30, 1943 2,450,580 Conzelman Oct. 5, 1948 2,583,404 Wyrfel Jan. 22,1952 2,704,394 Stewart: Mar. 22, 1955 FOREIGN PATENTS 723,208 FranceJan. 12, 1932

